Ng Cheuk-Yiu
Department of Chemistry, University of California, Davis, California 95616, USA.
Annu Rev Phys Chem. 2002;53:101-40. doi: 10.1146/annurev.physchem.53.082001.144416. Epub 2001 Oct 4.
The recent developments of vacuum ultraviolet (VUV) laser and third generation synchrotron radiation sources, together with the introduction of pulsed field ionization (PFI) schemes for photoion-photoelectron detection, have had a profound impact on the field of VUV spectroscopy and chemistry. Owing to the mediation of near-resonant autoionizing states, rovibronic states of ions with negligible Franck-Condon factors for direct photoionization can be examined by VUV-PFI measurements with rotational resolutions. The VUV-PFI spectra thus obtained have provided definitive ionization energies (IEs) for many small molecules. The recent synchrotron-based PFI-photoelectron-photoion coincidence experiments have demonstrated that dissociative photoionization thresholds for a range of molecules can be determined to the same precision as in PFI-photoelectron measurements. Combining appropriate dissociation thresholds and IEs measured in PFI studies, thermochemical data for many neutrals and cations can be determined with unprecedented precision. The further development of two-color excitation-ionization schemes promises to expand the scope of spectroscopic and chemical applications using the photoionization-photoelectron method.
真空紫外（VUV）激光和第三代同步辐射源的最新进展，以及用于光离子 - 光电子检测的脉冲场电离（PFI）方案的引入，对VUV光谱学和化学领域产生了深远影响。由于近共振自电离态的介导，对于直接光电离具有可忽略的弗兰克 - 康登因子的离子的振转电子态，可以通过具有旋转分辨率的VUV - PFI测量来研究。由此获得的VUV - PFI光谱为许多小分子提供了确定的电离能（IEs）。最近基于同步辐射的PFI - 光电子 - 光离子符合实验表明，一系列分子的解离光电离阈值可以以与PFI - 光电子测量相同的精度确定。结合在PFI研究中测量的适当解离阈值和IEs，可以以前所未有的精度确定许多中性和阳离子的热化学数据。双色激发 - 电离方案的进一步发展有望扩大使用光电离 - 光电子方法的光谱学和化学应用范围。
